Express to Venus

To mark completion of the assembly of the Venus Express spacecraft, Alenia Spazio is holding a Venus Express Day on 4 October in Turin, Italy, in cooperation with Astrium SAS and the European Space Agency.

Venus Express is the first European mission to this, the second planet in the Solar System. Often referred to as ‘Earth’s twin’, Venus holds many mysteries that intrigue scientists.

The main question is why a planet similar to Earth in size, mass and composition could have evolved so differently over the course of the last four billion years. Only 20 percent of the light that hits Venus makes it through the cloud cover, the other 80 percent of the Sun’s light is reflected back into space. This doesn’t make Venus a cold world, however, because the thick carbon dioxide atmosphere traps the planet’s heat. This greenhouse effect on Venus is often cited as a nightmare example of what could happen to Earth if we don’t get our pollution under control.

Venus up-close, as photographed by the Soviet Venera 13 lander, which parachuted to the Venusian surface on March 1, 1982Credit: Venera

Venus Express will make the first multispectral global examination of the atmosphere of Venus. Completely different from the one around Earth, the Venusian atmosphere appears to be hot and dense. Venus Express will investigate the choking ‘greenhouse’ effect, the hurricane-force winds that encircle the planet, and its mysteriously weak magnetic field.

David Grinspoon, a research scientist at the Southwest Research Institute in Boulder, Colorado, writes in his book, "Venus Revealed," that, through the Mariner 2 and other Venus missions, "we found our ‘sister planet’ to be chemically alien, as well as hot and dry to quite unearthly extremes. With these revelations, the twin-sister imagery quickly disappeared, and the notion that ‘Venus is hell’ took hold."

But Grinspoon told Astrobiology Magazine that more of Venus remains to be unshrouded: "For habitability, there are implications for Venus and there are implications for terrestrial planets in general. Venus almost certainly had liquid water when it was young. So the conditions for the origin of life, as conventionally defined, were satisfied there as much as on Earth and Mars."

Comparison of Mars, Venus and Earth in water bands, showing the clear presence of water on Earth uniquely Credit: NASA Workshop, Pale Blue Dot

Just as with Mars, tracking the history of water offers a common tie to habitability questions in the past noted Grinspoon: "The problem in thinking about the habitability of Venus is that, in the conventional view, the water didn’t last long. But if the water lasted for billions of years, that becomes much more interesting for the possibility of biological development. Earth is going to lose its oceans in the future, just as Venus did in the past."

Completion of assembly of the Venus Express spacecraft, including integration and testing of the flight equipment and experiments, is an important milestone. Scheduled for launch on 26 October 2005, Venus Express is currently being made ready for shipment to Astrium, ESA’s prime contractor, in Toulouse, France in mid-October this year. There, further tests to prove the spacecraft’s flight readiness will take place. Many of the components employed successfully on this year’s Mars Express mission will be applied to streamline next year’s planned journey towards the inner neighbor.

Grinspoon said, " I’m a strong advocate of new missions to Venus. We really have to go to the surface and dig in the rocks and drill to find out what is the mineralogy, and what is the history of the older areas in particular. …It’s not going to be easy, because Venus is a hard place. It’s a challenging place to explore on the surface, given the extreme conditions, and also because recent geological activity has destroyed the obvious signs of that older history…[Venus Express] will not address the surface issues, but it will do some really interesting orbital science."